Hydraulic lift for industrial trucks and tractors



March 17, 1959 A. w. GUNNING EI'AL 2,

HYDRAULIC LIFT FOR INDUSTRIAL TRUCKS AND TRACTORS Filed May 31. 1956 4Sheets-Sheet l INVENTORS 41.5950 WGwwvwa-AE BY flue/M4 DOE/"4N imm/ATTORNEY I Mega-ch 17, 1959 A. w. GUNNING ET AL 2,877,868

HYDRAULIC LIFT FOR INDUSTRIAL TRUCKS AND TRACTOR-S Filed May 31, 1956 4Sheets-Sheet 2 f8 we mw/ 4596 4 TTOK/VEY March 17, 1959 A. w. GUNNINGETIAL 2,877,868

HYDRAULIC LIFT FOR INDUSTRIAL TRUCKS AND TRACTORS Filed May 31. 1956 4Sheets-Sheet 3 March 17, 1959 Filed May A. w. GUNNING ETAL 2,877,868

HYDRAULIC LIFT FOR INDUSTRIAL TRUCKS AND TRACTORS 31, 1956 4Sheets-Sheet 4 4 INVENTORS v 44 FRED nlwv/w/vafi 442 BY 62/61/64 DOE/MANUnite HYDRAULIC LIFT FOR INDUSTRIAL TRUCKS AND TRACTORS Application May31, 1956, Serial No. 588,438

9 Claims. (Cl. 187-9) Our invention relates generally to industrialtrucks of the load-lifting and transporting type, and more particularlyto a new and improved hoisting mechanism capable of being adapted foruse with industrial trucks or tractors.

Our present invention comprises an improvement in the earlier structuredisclosed in U. S. Patent No. 2,514,052, issued to Alfred W. Gunning assole inventor.

According to a principal feature of our invention, we have provided alifting mechanism which may be readily adapted for use with a widevariety of vehicles of known construction, and which is capable oflifting a load from fioor level to a height greatly exceeding the normalinoperative height of the lifting mechanism. Such a feature greatlysimplifies the problems associated with storing the vehicle when not inuse, and it greatly facilitates load-handing operations in thoseinstances when the operating environment includes low ceilings andpassageways.

We are aware of various lifting mechanisms, including that of theabove-mentioned patent to A. W. Gunning, one of the instant jointinventors, which are capable of hoisting a load from one level toanother. These mechanisms are characterized by a hydraulic liftingcylinder and piston for actuating the mechanism, and the total distancetraveled by the load during operation exceeds the total movement of theactuating piston.

By way of illustration, the prior art lifting mechanism described in theabove-mentioned patent to A. W. Gunning comprises a pair oftelescopically related, vertically positioned sections defined bychannels or rails between which is mounted a hydraulic cylinder andpiston mechanism. I A lifting fork is carried at one side of thechannels, and it is adapted to ride therealong during loadliftingoperations. A complex chain and pulley arrangement is employed in theprior art arrangement for drivably connecting the lifting fork, one ofthe sections and the movable piston, the other section remaining fixedto the truck and serving as a reaction member. During the initial stagesof operation, the lifting fork is raised to the top of the channels bythe hydraulic piston as both of the sections remain stationary. Uponfurther move ment of the hydraulic piston, the lifting fork'remainsstationary with respect to the relatively movable sections while thelatter is being moved with respect to the fixed section. The maximumheight to which the load may be lifted is thus twice the height of thechannels when the mechanismis in the retracted position, but the liftingforce exerted by the hydraulic piston is three times the weight of theload since the mechanical lifting ratio is three to one. 1

When the above described patented structure is lowered or retracted, thereverse sequence is followed; i. e., the lifting fork is first loweredconjointly with the movable channels as the cylinder and piston isretracted, and then the lifting fork is lowered with respect to thefixed channels as the hydraulic piston is further retracted to theoriginal starting position.

Sttes Patent ice In order to make certain that the above sequence isfollowed, a complex latching mechanism must be incorporated in thepatented structure to prevent the movable channels from moving until thelifting fork reaches the upper extremity of the channels during alifting operation and to cause the lifting fork and the movable channelto move in unison during the initial stages of a lowering or retractingoperation.

The improved structure of our instant invention eliminates the need forsuch a latching mechanism and it is substantially less complex and morereliable in operation.

Further, the mode of the operation of the mechanism of our inventionembodies a new concept which overcomes the deficiencies inherent inconventional lifts.

The provision of such an improved hoisting mechanism 'being a principalobject of our invention, it is a further object of our invention toprovide a hoisting mechanism of the type above described which includesa plurality of telescopically related channel members and a liftingcarriage assembly operatively associated therewith and in which arelatively large movement of the lifting carriage will accompany arelatively small movement of the hoisting members of the mechanism, theratio between the maximum lifting height of the lifting carriage to thenormal retracted height of the mechanism being appreciably greater thanthe corresponding ratio inherent in structures of known construction.

It is a further object of our invention to provide a hoisting mechanismwherein this dimensional advantagemay be enjoyed with no increase in thelifting force of the hydraulic piston being required; i. e., for a givenratio between the weight of the load and the force requirements of thehydraulic cylinder and piston, the mecha-- nism of our instant inventionis capable of lifting a given.- load to a considerably greater heightthan that height: which could be obtained with a conventional lifting:mechanism of known construction.

A further object is to provide a hoisting mechanism as above set forthwherein an increase in the lifting height can be obtained without acorresponding increase in the height of mechanism when it assumes aretracted position. Indeed, the retracted height of our improvedmechanism is substantially less than that of conventional mechanisms inspite of this increased lifting height advantage.

It is a further object of our invention to provide a hoisting structureof the type set forth above wherein relative movement between each ofthe plurality of channels and the lifting fork takes placesimultaneously with an established ratio, each of the relatively movableelements of the mechanism reaching a terminal position simultaneouslyduring a load-lifting operation.

It is a further object of our invention to provide a hoisting mechanismof the type above set forth wherein the above described increased ratiobetween the maximum load-lifting height and the height of the retractedmechanism may be accomplished with no increase in the lifting ratio andwithout highly stressing any of the structural members of the mechanism.

It is a further object of our invention to provide a lifting mechanismcomprising telescopically related channels, a hydraulic piston and arelatively movable lifting fork, as above described, wherein separatepulley means are associated with each channel, the movable portion ofeach pulley means being situated at an elevated location thus preventingdirt and foreign matter from fouling the operation of the same. Thisfeature is of considerable significance when the mechanism is used inthe field or in warehouses, or the like, where scrap and debris islikely to accumulate.

Other objects and advantages of our invention will"- readily becomeapparent from the following descriptiow" newness In carrying forth theforegoing objects, we have provided a load hoisting mast comprising atleast three telescopically related sections defined by spaced parallelchannels, the lower or base sections being adapted to be secured in asuitable fashion to an industrial truck or tractor and held in fixedrelationship with respect to the other sections. A hydraulic pistonand'cylinder mechanism may be caused to actuate the first relativelymovable section or intermediate section and a pulley means is carried ata location proximate to the portion thereof on which the piston andcylinder mechanism acts. A first cable or chain may be trained over thepulley means and one end thereof may be anchored, the other end beingconnected to a third or upper movable section. The ratio between themovement of the piston and this last-mentioned movable section istherefore two to one.

The third movable section is slidably received within the intermediatesection and it also carries a pulley means at the upper end thereof overwhich a separate cable or chain is trained, one end of this second cableor chain being connected to the top side of the intermediate sections,and the other end of the second cable being connected to the liftingcarriage. The ratio between the movement of the lifting carriage and thehydraulic piston is therefore three to one.

According to another embodiment of our invention, a fourth relativelymovable section may be received within the third section and the cableor chain associated with the third section may instead be connected tothe fourth section. Another pulley means may be carried by the fourthsection and a third cable or chain may be trained thereover with one endthereof secured to the third section, the other end being connected tothe lifting carriage. The total movement of the lifting carriage whichmay be obtained with this embodiment will be equal to four times themovement of the piston, but the height of the mechanism in the retractedposition is still equal to the height of the above described firstembodiment. in each of the embodiments, duplicate pulleys and cables orchains are preferably provided for each of the movable sections and thisis the arrangement which will be described in the instant specification.

For the purpose of more particularly describing the principal featuresof our invention, reference will be made to the accompanying drawings,wherein:

Fig. 1 shows a side elevational view of an industrial truck or tractorutilizing the improved lifting structure of our instant invention, oneextreme elevated position being illustrated in Fig. l by dotted lines;

Fig. 2 is a plan view of the truck and lifting mechanism shown in Fig.i;

Fig. 3 is a front elevational view of the truck of Fig. 1, showing inmore particular detail the construction of the lifting mechanism of ourinstant invention;

Fig. 4 is a cross-sectional view of the lfting mechanism taken alongsection line 44 of Fig. 1;

Fig. 5 is a vertical cross-sectional view of the lifting mechanism takenalong section line 55 of Fig. 3;

Fig. 6 is a vertical cross-sectional view similar to that of Fig. 5wherein the telescopically related channels are shown in a partlyextended position;

Fig. 7 is a schematic representation of the lifting mechanism of ourinstant invention, showing the three operative positions;

Fig. 8 is a cross-sectional view similar to that of Fig. 5, showing amodified form of our invention;

Fig. 9 is a cross-sectional view of the modified construction of Fig. 8taken along section line 99 of Fig. 8;

Fig. 10 is a schematic representation of four operative positions of theload lifting structure of Figs. 8 and 9.

The first embodiment above described is illustrated in; Figures 1through 7 of the drawings, and the pulley arrangement forinterconnecting the relatively movable channels and the lifting fork ismore particularly illustrated in Figs. 5 and 6.

Referring first to Fig. linumeral 10 is used to generally designate atypical industrial type truck which includes a chassis 12, an engine 14suitably mounted on the chassis, front wheels 16, preferably of thetandem type, and dirigible rear wheels 18. A driver seat is illustratedat 20, and a portion of the vehicle controls are illustrated at 22 and24 adjacent the driver seat 20. A steering wheel 26 is mounted at theforward portion of the vehicle and may be pivotally connected to thedirigible wheels 18 through a suitable steering linkage, notillustrated.

The chassis 12 includes a vehicle frame upon which the lifting structureor mast of our instant invention may be mounted, said lifting structurebeing generally desig nated in the drawings by the numeral 28. A bracket30 may be pivotally mounted at a forward portion of the vehicle frame,and a pair of substantially rectangular outer channels 32 of a base mastsection may be secured thereto as indicated. A separate intermediatechannel may be slidably received within each outer channel 32 and theseintermediate channels may move relative to the base mast section to anupper position illustrated in Fig. 1 by means of dotted lines. Theintermediate channels define in part an intermediate mast section andthey are designated by the numeral 34. A pair of inner or upper channels36 of an upper mast section may in turn be slidably received within theintermediate channels 34, said channels 36 likewise being adapted to beextended to an upper position. This latter position is also illustratedin Fig. l by means of dotted lines.

A lifting fork or carriage assembly is illustrated in the drawings at 38and it includes a substantially horizontal pair of fork arms 40 and apair of right-angle mounting plates 42. A pair of rollers is designatedby numeral 44, each roller being mounted at a separate vertically spacedposition. The rollers 44 are received within the above mentioned innerchannels 36, one pair of rollers being associated with each channel 36.

A pair of brackets 47 is secured to the outer channels 32, one bracket48 being joined to each supporting channel, and a piston rod 49 may bepivotally connected to each bracket 48. The piston rod 49 forms aportion of a hydraulic cylinder and piston mechanism generallydesignated by numeral 51, the base of the mechanism 51 being pivotallymounted on the structural portion of the chassis 12 as illustrated at53. One hydraulic piston and cylinder mechanism 51 is provided for eachof the channels 32 at transverse locations on the vehicle as best seenin Fig. 2.

The two positions of the lifting fork illustrated in Fig. 1 representthe two extreme lifting positions, the upper eX- treme position beingillustrated by dotted lines. However, it will be appreciated that thelifting fork 38 may assume any of a plurality of intermediate positionsas desired between the two extreme positions illustrated. Duringoperation, the mast 28 may be pivoted about the connection between thechassis and the bracket 30 by extending or retracting the piston rod 49.Suitable hydraulic controls may be provided for this purpose to effectsuch a tilting operation.

Referring next to Figs. 2, 3, and 4, the structural relationship betweenthe channels and the lifting fork may be more fully understood. As bestseen in Fig. 4, each of the channels 32, 34, and 36 are formed withprogressively decreasing dimensions to accommodate a nestingrelationship therebetween. The rollers 44 are adapted to move verticallywithin the inner channel 36 for the purpose of guiding the lifting fork38. By preference, the lifting fork 38 includes a pair of horizontallyextended bars 46 to facilitate the handling of freight or other bulkymerchandise and the plates 42 may be secured thereto as-indicated. Thelower end of the outer channels 32 maybe joined by a lower supportingplate. 48 asillustratedin Fig. 4, and the lower end of the channels 34and 36 may similarly be joined by supporting plates 50 and 52respectively, the plates 48, 59 and 52 being situated in verticallystacked relationship when the channels assume the position lllustratedin Fig. 3. A central portion of each of the supporting plates 50 and 52is recessed, as illustrated at 54 and 56 respectively, for accommodatinga hydraulic cylinder and piston mechanism generally designated by thenumeral 58, said mechanism being vertically mounted on the lowersupporting plate 48 of the outer channels 32.

As best seen in Figs. 2 and 4, the carriage assembly 38 includes a pairof roller supporting members 60. The supporting members 68 may besecured to the carriage assembly 38 in any suitable fashion, as bywelding 62, and by preference, a supporting plate 64 is interposedbetween the members 60 to provide transverse support and to provide ameans for connecting thereto a lifting cable or chain which willsubsequently be described. The upper end of the channels 32 may beinterconnected by a hydraulic cylinder supporting bracket 66 and theupper end of the inner channels 36 may be interconnected by a supportingbracket 68.

Referring next to Fig. 3, the hydraulic cylinder and piston mechanism 58may be seen in more particular detail, and it includes a ram or pistonrod 70 which is adapted to engage a bracket 72 which interconnects theupper ends of the second pair of channels 34. It is seen from Fig. 3that a pair of pulleys 74 is mounted on the upper supporting bracket 68and a second pair of pulleys 76 is mounted on the bracket 72. A separateflexible member such as a cable or chain 80 may be trained over each ofthe pulleys 76 and one of the ends of each cable or chain may beanchored to a flange 78 carried by the upper end of the relatively fixedcylinder of the piston and cylinder mechanism 58.

Referring next to Figs. 5 and 6, the pulley arrangement previouslymentioned is illustrated in more particular detail and it will beapparent that each of the pulleys 74 and each of the pulleys 76 areprovided with a separate flexible member such as a chain or chains orcables, the cable associated with the pulleys 74 being shown at 80 asabove indicated, and the chain or cables associated with the pulley 76being shown at 82. The above-mentioned connection between the chains orcables 82 and the relatively stationary cylinder of the piston andcylinder mechanism 58 is shown in Figs. 5 and 6 at 84. For convenience,the flexible members will hereinafter be referred to as cables.

By preference, the above-mentioned supporting bracket 66 is formed withan extension 86 situated above the upper end of the piston and cylindermechanism 58 to provide an anchor support for the cables 82 at 84 and tomaintain the piston and cylinder mechanism in a fixed vertical position.Also by preference, the supporting bracket 66 is formed with asubstantially channel shape to provide added rigidity to the mechanism.

It may also be seen from Figs. 5 and 6 that the pulleys 76 are mountedat the upper end of the intermediate channels 34 by means of a mountingbracket 88 which may be permanently fixed to supporting bracket 72 in asuitable fashion. The lower ends of cables 82 are connected to thesupporting plate 52 at the lower end of the inner channels 36, saidconnection being designated in Figs. 5 and 6 by the numeral 90.

By preference, the pulleys 74 are situated in tandem at the upper end ofthe inner channels 36 and are mounted on the supporting bracket 68 by asuitable mounting bracket 92. The cables 80 are drawn over the tandempulleys 74 and one end of each cable 80 is fixed to the supportingmember 72, as shown at 94. The other end of each cable 80 is joined tothe supporting plate 64 of the carriage assembly 38 as illustrated at96.

For purposes of illustration, it will be assumed that the hydraulicpiston and cylinder mechanism is movedto a partly extended position asillustrated in Fig. 6. Since the cylinder of the piston and cylindermechanism is connected to the relatively fixed outer channels 32, andsince the movable piston rod 70 engages the supporting bracket 72 of theintermediate channels 34, movement of the piston rod with respect to thestationary fixed channels 32 will cause the channels 34 to move to apartly extended position in telescoping relationship. This relativemovement of the channels 34 causes the pulleys 76 to move in an upwarddirection and this upward movement is transmitted to the inner channels36 through the cables 82. Since one end of each cable 82 is anchored at84, the rate of movement of the inner channels 36 will be twice that ofthe intermediate channels 34. However, the movement of each of thechannels 34 and 36 occurs simultaneously although the rates of movementdifier by this constant ratio. Therefore, for any given displacement ofthe piston rod 70, the inner channels 36 will have moved to a heightwhich is twice that of the intermediate channels 34. This upwardmovement of the inner channels 36 causes a corresponding upward movementof the pulleys 74 and this motion is transmitted to the carriageassembly 38 through the cables since one end of each cable 80 isconnected at 94 to the intermediate channels 34 while the other end isconnected to the carriage assembly.

The operation of the mechanism and the pulley arrangement may be readilyunderstood by referring to Fig. 7 wherein three operative positions ofthe lifting mechanism are illustrated. It is emphasized that the pulleyarrangement at one transverse side of the vehicle is identical to thaton the other side. It is apparent upon an inspection of Fig. 7 that asthe piston rod 70 is moved from the first position to the secondposition, the movement of the intermediate channels 34 will be exactlyequal to the displacement of the piston rod. However, since the liftingratio between the intermediate channels 34 and the inner channels 36 isexactly two to one, the inner channels 36 will be moved a distance whichis twice that of the intermediate channels 34. However, the liftingratio of the intermediate channels 34 with respect to the carriageassembly is not two to one since the cables 80 are connected to a memberwhich moves with respect to the channels 36 at a predetermined ratio.The lifting ratio of the inner channels 36 with respect to the carriageassembly is therefore decreased by the extent of this predeterminedratio, the overall lifting ratio between the carriage assembly and thepiston rod therefore being exactly three to one.

The third illustration shown in Fig. 7 shows the piston rod 70 in afully extended position. Since the lifting ratio is three to one, aspreviously described, the carriage assembly will assume a position whichis exactly three times the distance that the piston rod travels. For thepurpose of illustrating the above described lifting advantage, we havedeveloped one working embodiment of our improved mechanism in which theoverall retracted height of the mechanism is eighty inches (80") andwherein a total fork height of one hundred and sixty-two inches (162)may be obtained. Similarly, in another operative embodiment of ourinvention in which the overall height is ninety-two inches (92"), atotal fork height of one hundred and ninety-eight inches (198") may beobtained. By way of contrast with the lifting mechanism disclosed in theabove mentioned patent to A. W. Gunning, the overall height of theupright structure disclosed in the patent is equal to eighty-threeinches (83") in the collapsed position, but the lifting fork can beraised from ground level to only sixty-three inches (63") during theinitial stages offthe lifting operation, and to a final height of onlyone hundred and thirty inches,

Referring next to the second embodiment of our invention illustrated inFigs. 8 through 10, four telescopically related rectangular mastsections are provided v relative motion between the channels rather thanthree mast sections as in the previous embodiment, each section beingdefined by nested channels and the outermost channels being designatedby numeral 200; the second channels being designated by numeral 202; thethird channels being designated by numeral 204, and the innermostchannels being designated by numeral 206. A pair of rollers is situatedwithin the innermost channels 206 as shown at 208 and they form aportion of a lifting fork structure or carriage assembly similar to thatpreviously described. The carriage assembly of the embodiment of Figs. 8through 10 is generally designated by numeral 210. The lower ends of theouter channels 200 are joined together by supporting plate 212 and eachof the other channels 202, 204 and 206 are joined at the lower endsthereof by similar supporting plates 214, 216 and 218 respectively.

A hydraulic cylinder and piston mechanism 220 is mounted, as in theprevious embodiment, on the lower supporting plate 212, the supportingplates 214, 216 and 218 being recessed at an intermediate locationthereon to accommodate the piston and cylinder mechanism 220. It isemphasized that the hoisting mechanism of Figs. 8 through 10 may bemounted on an industrial truck or tractor in the manner previouslydescribed in connection with the previously described embodiment.

Referring more particularly to Figs. 8 and 10, it may be seen that theouter channels 200 are joined adjacent the upper ends thereof by asupporting member 222, preferably of channel-shape, which includes anextension 224 situated adjacent the top of the piston and cylindermechanism 220 for supporting the same. The next pair of channels 202includes a supporting member 235 which bridges the upper ends thereofand which carries pulleys 228 suitably mounted on a pulley bracket 230.Similarly, the channels 204 and 206 are formed with supporting members232 and 234 respectively, the supporting member 232 having mountedthereon another set of pulleys 236 and the supporting member 234 havingmounted thereon a third set of pulleys 238. Each of the pulleys 228, 236and 238 are preferably of the tandem type.

A first cable 240 may be drawn over each of the pulleys 22S and one endof each cable 240 may be anchored to the relatively stationary channels200, as shown at 242. The other end of each cable 240 is joined at 247to the supporting plate 216 of the channels 204. A second cable 245 maybe drawn over each of the pulleys 236 and one end of each cable 245 maybe joined to the supporting member 235, as shown at 244, the other endthereof being connected to the mounting plate 218,

as shown at 246, thereby imparting a lifting motion to the innerchannels 206. Finally, a third cable 248 may be drawn over each of thepulleys 238 and one end of each cable 248 may be connected to a mountingplate 232 as shown at 290, the other end thereof being con nected to thecarriage assembly 210 as shown at 252.

It will thus be apparent that the pulley arrangement of the embodimentof Figs. 8 through 10 is substantially similar to that of the previouslydescribed embodiment. However, it is capable of further multiplying themotion of the hydraulic piston and cylinder mechanism 220 by reason. ofthe additional mast section which is provided. The piston rod of thepiston and cylinder mechanism 220, shown at 254, acts directly on thechannels 202 and the 200 and the channels 202 during operation isexactly equal to the relative movement between the piston rod 254- andthe relatively stationary portion of the piston and cylinder mechanism.

The operation of the embodiment of Figs. 8 through l'.) may best beobserved by referring to the schematic representation of Fig. 10. Forpurposes of clarity, we have illustrated four operative positions of themechanism in order to provide amore complete understanding of the same.

Referring first to the first operative position illustrated in Fig. 10,it will be observed that the overall stacked height of the mechanism issubstantially the same as that of the previous embodiment. If it isassumed that the piston rod is extended from the position shown in thefirst illustration to that shown in the second illustration, the motionimparted to the channels 202 will be exactly equal to the movement ofthe piston rod.

Since the lifting ratio of the cable 240 and the pulleys 228 is two toone, and since one end of each cable 240 is anchored, the channels 202will move a distance exactly twice that of the distance traveled by thepiston rod. If this latter distance is represented by the symbol x, thedistance traveled by the channels 202 will therefore be 2x. Since thelifting ratio of the cables 245 and the pulleys 236 with respect to thechannels 202 is two to one, and since the channels 202 move at apredetermined ratio with respect to the channels 200, the distancetraveled by the channels 204 as the piston rod moves a distance x willbe equal to the quantity (4x 1x) or 3x. Similarly, the lifting ratio ofthe pulleys 238 and the cables 248 with respect to the channels 204 istwo to one. However, as in the previous case, the channels 204 moverelative to each of the channels 200 and 202 at separate predeterminedfixed ratios. Therefore, the motion which is imparted to the liftingfork by the innermost channels 206 and the associated cable will beequal to the quantity 2 (4x 1x)2x or 4x. Therefore, it is seen that theoverall lifting ratio of the second embodiment of Figs. 8 through 10 isexactly equal to four to one.

As the piston rod 254 moves to a further extended position, the carriageassembly will continue to rise at a rate four times the rate of movementof the piston rod and each of the channels 200 through 206 will movesimultaneously at their own fixed ratios until the ultimate positionillustrated in the fourth operative position of Fig. 10 is obtained. Theoverall height of the lifting fork in this ultimate position will beapproximately three times the original stacked height shown in the firstillustration.

As previously indicated, the cables illustrated in the drawings may bereadily replaced by chains if desired, the extent of the modificationrequired to accomplish this being slight.

We are aware that various changes may be made in certain details of theconstruction specifically shown herein without departing from theprinciples of our invention and we therefore do not intend that thescope of our invention should be limited except as defined by the scopeand spirit of the appended claims.

What We claim is:

1. A load hoisting mast comprising a stationary base mast section, aplurality of movable mast sections said mast sections being arranged insubstantially vertical telescopic relationship, a hydraulic cylinderconnected to said base section, a piston movably positioned in saidcylinder, a piston rod secured to said piston, said piston rod beingconnected to the lowermost one of said plurality of movable mastsections, plural pulley means carried by each of said movable mastsections at the upper portion thereof, a separate flexible membertrained over each pulley means, a first end of each flexible membertrained over the pulley means carried by the lowermost one of saidplurality of movable mast sections being anchored to a relativelystationary portion of said mast, a first end of each of the otherflexible members trained over the pulley means carried by each of theother movable mast sections being connected to the upper portion of thenext lower movable mast section, a lifting carriage movably carried bysaid mast, the second end of each flexible member trained over thepulley means carried by the uppermost one of said movable mast sectionsbeing connected to said lifting carriage to effect vertical movement ofthe same, the second end of each aeraeee flexible member trained overthe pulley means carried by each of the other movable mast sectionsbeing connected to the lower portion of the next upper movable mastsection, the movement of said carriage being continuously and directlyrelated to the movement of said piston by a fixed motion transmittingratio which is equal in magnitude to the number of said telescopicallyrelated mast sections.

2. A load hoisting mast comprising a base mast section, an upper mastsection and one intermediate mast section, said mast sections beingarranged in substantially vertical telescopic relationship, a hydrauliccylinder connected to said base section, a piston movably positioned insaid cylinder, a piston rod secured to said piston, said piston rodbeing connected to said intermediate section, first pulley means carriedby said intermediate section at the upper portion thereof, a firstflexible member trained over said first pulley means with one endthereof anchored to a relatively stationary portion of said mast andwith the other end thereof connected to a lower portion of said uppersection, a second pulley means carried by said upper section at theupper portion thereof, a second flexible member trained over said secondpulley means with one end thereof connected to said intermediatesection, and a lifting carriage movably carried by said mast, the otherend of said second flexible member being connected to said liftingcarriage to effect vertical movement of the same, the movement of saidcarriage being continuously and directly related to the movement of saidpiston by a fixed motion transmitting ratio which is equal in magnitudeto the number of said telescopically related mast sections.

3. A load hoisting mast comprising a base mast section, an upper mastsection and two intermediate mast sections, said mast sections beingarranged in substantially vertical telescopic relationship, a hydrauliccylinder connected to said base section, a piston movably positioned insaid cylinder, a piston rod secured to said piston, said piston rodbeing connected to a first of said intermediate sections, first pulleymeans carried by said first intermediate section at the upper portionthereof, a first flexible member trained over said first pulley meanswith one end thereof anchored to a relatively stationary portion of saidmast and with the other end thereof connected to a lower portion of asecond of said intermediate sections. a second pulley means carried bysaid second intermediate section at the upper portion thereof, a secondflexible member trained over said second pulley means with one endthereof connected to said first intermediate section and with the otherend thereof connected to a lower portion of said upper section, a thirdpulley means carried by said upper section at the upper portion thereof,a third flexible member trained over said third pulley means with oneend thereof connected to said second intermediate section, and a liftingcarriage movably carried by said mast, the other end of said thirdflexible member being connected to said lifting carriage to effectvertical movement of the same, the movement of said carriage beingcontinuously and directly related to the movement of said piston by afixed motion transmitting ratio which is equal in magnitude to thenumber of said telescopically related mast sections.

4. A load hoisting mast comprising a base mast section, an upper mastsection and an intermediate mast section, said mast sections beingarranged in substantially vertical telescopic relationship, motor meansfor imparting relative motion between said base section and saidintermediate section, said motor means having two relatively extensibleparts, one of said parts being con nected to said base section and theother part being connected to said intermediate section, first pulleymeans carried by said intermediate section at the upper portion thereof,a first flexible member trained over said first pulley means with oneend thereof anchored to a relatively stationary portion of said mast andwith the other end thereof connected to a lower portion of said uppersection, a second pulley means carried by said upper section at theupper portion thereof, a second flexible member trained over said secondpulley means with one end thereof connected to said intermediatesection, and a lifting carriage movably carried by said mast, the otherend of said second flexible member being connected to said liftingcarriage to effect vertical movement of the same, the movement of saidcarriage being continuously and directly related to the relativemovement of the parts of said motor means by a fixed motion transmittingratio during the entire operating time interval.

5. The combination as set forth in claim 2 wherein each mast sectioncomprises a pair of channels, supporting means for maintaining thepaired channels of each section in spaced, parallel relationship, thecorresponding channels of each mast section being disposed one withinthe other in nesting relationship.

6. The combination as set forth in claim 5 wherein the outermostchannels define in part said base section, wherein the innermostchannels define in part said upper section and wherein said oneintermediate section is defined in part by the channels situated betweenthe innermost and outermost channels.

7. The combination as set forth in claim 5 wherein said carriageincludes rollers disposed within and movable along the innermostchannels, said carriage thereby being guided during load hoistingoperations.

8. The combination as set forth in claim 5 wherein said cylinder isconnected to and supported by the supporting means for the channels ofsaid base section.

9. The combination as set forth in claim 5 wherein the supporting meansfor said intermediate section and said upper section each comprises abracket connecting the upper ends of the respective channels thereof,the pulley means for each of said last mentioned sections beingconnected to the respective bracket thereof.

References Cited in the file of this patent UNITED STATES PATENTS1,311,165 Hennessy July 29, 1919 2,394,458 Lull Feb. 5, 1946 2,571,858Garland Oct. 16, 1951 2,632,530 Wagner Mar. 24, 1953 2,701,031 BrumbaughFeb. 1, 1955 2,787,343 Mitchell Apr. 2, 1957 FOREIGN PATENTS 722,766Great Britain Jan. 26, 1955

